1. Field of the Invention
The present invention relates to an improved valve handle, more particularly, to a valve handle that prevents a valve from being accidentally turned on.
2. Description of the Prior Art
In the process of semiconductor wafer production, various kinds of gasses are required at each stage of the manufacturing process. For instance, in a CVD process, the commonly used gasses are SiH4, B2H6, NH3, and hydrogen gas; in a dry etching process, the gases used are CF4, CHF3, oxygen, and SF6; and in an ion implantation the gases used are PH3, BF3, other frequently used inert gases, etc. Some of these gases are toxic, like PH3 and BF3; some are explosive, such as SiH4, with a threshold limit value (TLV) of 0.5 ppm and an explosive energy that is 6 times greater than the conventional explosive TNT. A well designed gas-transportation system for delivering processing gases is mandatory for each wafer production process, and the design of the gas-transportation system will vary with the characteristics of the various types of gases. When dealing with toxic or explosive processing gases, extreme care must be taken to avoid explosions or poisonings due to leaking gas.
Valves are the most commonly seen aspect of a gas transportation system. The purpose of the valves is to control the gas flow, so it is indispensable in the entire production system: from the gas source through many transportation routes, to the reactor and then to an exhaust. Valves can be grouped into two categories based on use: 1) ON/Off type and 2) adjustable type. An ON/OFF valve is used to stop gas flow under certain conditions, such as during maintenance of transportation routes.
Please refer to FIG. 1. FIG. 1 is a partial view of a cross-section of a valve used in wafer production processes according to the prior art. As shown here, the valve is a typical diaphragm valve commonly found on the market. The flow control of a processing gas for the valve 10 takes place between the flow passages 21 and 22. Briefly, gas flow control is achieved by a valve base 31, which is made from poly-chloro-trifluoroethlene (PCTFE), and by a diaphragm 32, both of which are located in the vicinity of the opening of the flow passage 21. The diaphragm 32 moves up and down to open and close the flow passage 21, and the up and down movement is driven by the stem 41 and the handle 42.
The stem 41 and the handle 42 of the conventional valve 10 are fastened together with bolts or by welding. As an operator turns the handle 42, the stem 41 moves up or down, which mobilizes the diaphragm 32, to which the stem 41 is connected, so as to turn on or off the valve 10. For instance, when the operator turns the handle 42 clockwise, the diaphragm 32 moves down and stops the flow of the processing gas. Conversely, when the operator turns the handle counterclockwise, the diaphragm goes up and thus turns on the valve 10. However, although the on/off state is displayed on the handle 42 of the diaphragm valve 10, mistakenly turning on a valve in some section of the gas transportation system occurs, and not infrequently in a wafer production factory that has hundreds or thousands of valves. As toxic or explosive processing gases can escape into the air due to an improper valve state (i.e., open or closed), the safety of the working environment the lives of workers are put at risk.
It is therefore a primary objective of this invention to provide an improved manual valve to solve the problem described above.
Another objective of the invention is to provide a valve handle that prevents the valve from being accidentally turned on so as to ensure the safety of the working environment.
In the preferred embodiment of the present invention, a valve handle, which prevents a valve from being mistakenly turned on, has a fixing ring for driving a stem up and down, the fixing ring having at least one stopper. The valve handle also has a knob housing that covers and turns the fixing ring. The knob housing has at least one protrusion located on a top inner side of the housing that works with the stopper of the fixing ring. The protrusion comprises a first perpendicular plane and a slant plane.
When an operator turns the knob housing in a first turning direction, the first perpendicular plane pushes the stopper, causing the fixing ring to turn in the first turning direction and simultaneously making the stem descend, placing the valve in an OFF state. When an operator turns the knob housing in a second turning direction, the slant plane slides past the stopper, and so is unable to move the fixing ring, and the valve at this time cannot be turned to an ON state.
It is a benefit of the present invention that the interaction of the perpendicular and slant planes prevents the valve of the valve from being easily opened. Hence, the valve is less likely to be mistakenly opened by an operator, and thus the dangerous leakage of gasses associated with such mistakenly opened valves can be avoided.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.